Maths: Doubling and halving. Double the following numbers: a) 268 b) 341. Halve the following numbers: a) 436 b) 78

$$268 \times 2 = 536$$

The doubled number is $\boxed{536}$.

b) 341

$$341 \times 2 = 682$$

The doubled number is $\boxed{682}$.

Halve the following numbers:

a) 436

$$\frac{436}{2} = 218$$

The halved number is $\boxed{218}$.

b) 78

$$\frac{78}{2} = 39$$

The halved number is $\boxed{39}$.